1. Field of the Invention
This invention relates to laminates. In one aspect, the invention relates to laminates having an intermediate binding layer of polyalkylenepolyamine. In another aspect, the invention relates to a method of preparing these laminates.
2. Description of the Prior Art
Branched chain polyethylenimine (PEI), as exemplified in I, has long been an art-recognized intermediate binding layer for various laminates. ##STR1## Illustrative teachings include: Lacy et al., USP 3,140,196 (non-aromatic polyolefin or vinylidene chloride and vinyl chloride copolymer film laminated to various metal foils); Lacy et al., U.S. Pat. No. 3,033,707 (non-aromatic polyolefin film bonded to vinylidene chloride and vinyl chloride copolymer-coated cellophane); Newmaker, U.S. Pat. No. 3,096,602 (non-aromatic polyolefin film bonded to a nonregenerated cellulose base); and Br. 919,065 and Hurst U.S. Pat. No. 3,230,135 (non-aromatic polyolefin film bonded to paper and paperboard).
PEI has a wide variety of amine functionality and is thus cationic in character. As such, PEI has a high affinity for various anionically charged substrates, e.g., cellulose, glass, various metals and the like. This affinity for anionic sites is a major property leading to its utility as a laminate adhesive. Accordingly, it has generally been thought that compounds without this wide variety of amine functionality would have little, if any, utility as laminate adhesives.